Proper engine timing--that is, the timing of the spark relative to the position of the piston within each cylinder--is important for proper engine performance. Engine performance can be modified significantly by slighting changing the timing of the spark. As such, it is desirable to be able to finely adjust the engine timing.
Various engine-timing plates are known in the prior art. As it is convenient to modify the ignition timing of the spark at the distributor assembly, most such timing plates are designed for installation at the distributor. For example, U.S. Pat. No. 4,744,339 to Nagai et al. on May 17, 1988, illustrates such a device (FIG. 7), as does U.S. Pat. No. 4,177,781 to Marchelletta et al. on Dec. 11, 1979; U.S. Pat. No. 4,058,691 to Wittner on Nov. 15, 1977; U.S. Pat. No. 3,906,920 to Hemphill on Sep. 23, 1975; and U.S. Pat. No. 3,660,623 to Bevacqua on May 2, 1972. All of these prior art devices illustrate adjustable timing plates for various types of distributor assemblies. Typical of such devices is a slotted mounting hole that permits limited movement along an arc for adjusting the timing of the spark relative to a rotor member.
A considerable drawback to all such prior art timing plates is that there is no means of referencing the location of the plate to the distributor assembly. As a result, if the timing plate over time becomes shifted from its original position, such shifting is difficult to detect with the eye. Further, with no referencing means between the timing plate and the distributor assembly, it is difficult to know by how much to adjust the timing plate to advance or retard the timing of the spark by a given amount. As a result, such timing plates of the prior art are difficult to adjust accurately and in a trial-and-error type of manner. The present invention fulfills these needs and provides further related advantages.